Scientists breed ‘allergen-free’ milk cow

Genetically modified cow Daisy grazes in a pasture on Monday.

Photo: AFP / Agresearch

A genetically modified cow whose milk lacks a substance that causes allergic reactions in people has been created by scientists in New Zealand.

In their first year of life, two or three in every hundred infants are allergic to a whey protein in milk called BLG, or beta-lactoglobulin protein. The researchers engineered the cow, called Daisy, to produce milk that does not contain BLG.

The genetic alteration slashed levels of BLG protein in the cow’s milk to undetectable levels.

The cow was created with the same cloning procedure that led to the creation of Dolly the sheep in 1996 and was delivered by caesarean at a government-owned AgResearch lab in Hamilton.

Stefan Wagner, a scientist on the team, said they now plan to investigate whether or not the BLG-free milk causes allergic reactions.

The work also drew on a technique that gives scientists control over which genes are active in an animal and gives fresh momentum to plans to engineer animals that are more resilient to diseases.

To make Daisy, scientists took a cow skin cell and genetically modified it to produce molecules that block the manufacture of BLG protein. The nucleus of this cell was then transferred into a cow egg that had its own nucleus removed.

The reconstituted egg was grown in the lab until it formed what is called a blastocyst, a ball of around 100 cells, and then transplanted into the womb of a foster cow.

The cloning technique is not efficient. Of around 100 blastocysts the scientists implanted into cows, more than half of the pregnancies failed early on, and only one live calf, Daisy, was born.

Bruce Whitelaw, professor of animal biotechnology at the Roslin Institute at Edinburgh University, said the major advance was demonstrating that the genetic procedure, called RNA interference, works in large animals.

One question the New Zealand team is working on now is why Daisy was born without a tail. The cloning process, not the extra genes, is most likely to blame.